The present invention relates to an antiglare or low beam headlamp for motor vehicles, particularly for a rectangular reflector type headlamp. Headlamps of this type to be permitted in the U.S.A. must generate a lower beam whose light distribution corresponds to the U.S. rule J 579 c. This lower light beam for illuminating a roadway is shaped both by the configuration of the reflector and by optical means provided on the light diffusing glass in the aperture of the reflector.
For technical and optical reasons in manufacturing a headlamp, the reflector is usually made with a simple configuration to reflect an untreated or initial light beam; in order to obtain from the initial light beam a lower or dimmed light beam the optical means must perform different functions and this requirement complicates the manufacture of the light diffusing glass and causes a substantial deviation of the dimmed light beam from the prescribed light distribution.